Histogenesis and tissue reconstruction of mixed mesodermal tumor.

The clonal cell lines designated as HIRS-BMS and HIRS-BMA were established from HIRS-BM (multipotent primitive cells which differentiated into rhabdomyosarcoma and adenocarcinoma cells) by a single cell plating method. The HIRS-BMS was a rhabdomyosarcoma cell line composed of elongated fibrous cells which contained myoglobin. The HIRS-BMA was an adenocarcinoma cell line composed of round cells. The tissue reconstruction of these cell lines was studied in vitro (rotation culture system) and in vivo (transplantation into hamster cheek pouch). The HIRS-BMS cells produced rhabdomyosarcoma, both in vitro and in vivo, and the HIRS-BMA produced poorly differentiated adenocarcinoma, in vitro and in vivo. The mixture of HIRS-BMS and HIRS-BMA produced a mixed mesodermal tumor resembling the original tumor. These results support the theory of a combined tumor as a cause of mixed mesodermal tumor.